Stability and Electron Affinities of Negatively Charged Aluminium Clusters: A Computational Study

A computational study on the stability of neutral, singly and doubly negatively charged aluminium clusters Al-n(z), with n = {13, 18, 23, 39, 55}, and z = {0, -1, -2} is presented. Estimates of electron affinities (EA) were computed with (i) all-electron quantum-mechanical calculations with full geometry optimization on Alnz, with n = {13, 18, 23, 39, 55}, and z = {0, -1, -2), using the Perdew-Burke-Ernzerhof (PBE) gradient-corrected functional within Density Functional Theory (DFT) and (ii) Charged Conducting-Sphere Model with and without Coulomb barrier and tunnelling corrections. If a positive value for the second electron affinity of the cluster is considered to be the sole criterion for the production and experimental observation of dianionic aluminium clusters, then the predicted minimum cluster size (i.e. the number of atoms) is n similar to 23 and n similar to 32 from the all-electron computations and the charged conducting-sphere model, respectively.